1. Field of the Invention
The present invention relates generally to audio reproductions and specifically to the enhancement of the audio experience by introducing phantom bass.
2. Related Art
In many audio systems, such as in a laptop computer, the speakers are limited to frequencies above a given threshold frequency. Either the speaker cannot reproduce audio frequencies below the given threshold or is prevented from producing audio frequencies below the given threshold. Often, speakers are prevented from operating below the given threshold frequency because low frequencies can cause detrimental effects to the device. For instance, there is a suspicion in the industry that low frequencies produced by a laptops audio system can degrade the life of a hard disc.
FIG. 1 illustrates a typical audio system used in devices such as laptop computers. The audio driver comprises high pass filter 102 which attenuates frequencies below a given threshold, digital to audio converter (DAC) 104 which converts a digital signal into an analog signal, and analog stages 106 which drive speaker 108. Analog stages 106 often comprise an amplifier and an output stage. In other audio systems an analog high pass filter is used instead of high pass filter 102 and placed after DAC 104 in the audio path.
However, because frequencies below a given threshold are suppressed, the listener may experience a lack of “bass.” Techniques known as “phantom bass” or “virtual bass” are used to reconstitute the bass lost due to the suppression of low frequencies in the audio signal.